1. Technical Field
The invention relates generally to semiconductor devices, and more particularly, to a substrate having hybrid crystallographic surface orientations in one or more semiconductor-on-insulator (SOI) regions and/or non-SOI regions for supporting different semiconductor devices.
2. Background Art
Performance improvement of semiconductor devices is a never-ending endeavor for manufacturers of those devices. One challenge currently faced by the semiconductor industry is implementing different semiconductor devices, e.g., memory and logic devices, on a single chip while maintaining process simplicity and transistor performance. These devices are referred to as “system-on-chips” (SoC) because the electronics for a complete, working product are contained on a single chip. One approach that is currently employed to improve performance of a SoC is to fabricate the different types of semiconductor devices on silicon substrates having optimal surface orientations. As used herein, “surface orientation” refers to the crystallographic structure or periodic arrangement of silicon atoms on the surface of a wafer. Different surface orientations are optimal for different semiconductor devices. For example, an n-type field effect transistor (nFET) can be optimized by being generated on silicon having a <100> surface orientation, while a p-type FET (pFET) can be optimized by being generated on silicon having a <110> surface orientation. In addition, memory devices and nFETs are typically optimized when generated on semiconductor-on-insulator (SOI) substrates, while pFETs are typically optimized when generated on bulk silicon substrates.
One approach to providing these substrates includes bonding two substrates having different surface orientations to one another, with an insulative silicon dioxide (oxide) layer in between to form an SOI substrate. However, there is a need in the industry for both SOI and non-SOI areas on a single substrate for specific applications. These applications may include, for example, power devices or devices where a thick silicon substrate allows for desired strain from features such as embedded silicon germanium (SiGe) or the like. It also may be desirable to have more than one thickness of silicon over the buried oxide.
In view of the foregoing, there is a need in the art for a substrate having different surface orientations and different structure, e.g., SOI and non-SOI regions.